#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int cmp(const void* a, const void* b)
{
	return *(char*)a - *(char*)b;
}

int main()
{
	char* str = (char*)malloc(1001 * sizeof(char));
	scanf("%s", str);
	qsort(str,strlen(str), sizeof(char), cmp);
	puts(str);
	return 0;
}